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Shedding Light on the Dark Side of the Universe


Licia Verde remembers a book she got as a child that taught her the basics about everything from the atmosphere and weather to the solar system and the galaxy. The book began her fascination with cosmology and showed what was to come. But Verde's potential wasn't apparent early on. "In school I wasn't really good at math," admits Verde. She chose a high school, in her hometown of Venice, Italy, that emphasized literature, art, and language.

Today, Verde studies dark energy, dark matter, and how the universe formed and continues to evolve, as an assistant professor of physics and astronomy at the University of Pennsylvania (UPenn). In contrast to the mysterious forms of energy and matter she studies, the 33-year-old Verde radiates enthusiasm when talking about her work. "I never stop being amazed by it," she says.

Fulfilling Her Destiny

In high school, Verde only had math and physics lessons for an hour or two a week. But that brief exposure to physics was sufficient to reinvigorate her interest in cosmology. She decided to pursue physics at the University of Padova, but she knew she had some catching up to do. So she taught herself from a high-school math book and brought herself up to speed in just 6 months.

The independent study gave Verde a mathematical foundation that enabled her to excel in physics, having written an undergraduate thesis on the relationship between the clustering of dark and luminous matter, and splitting her time between Padova and the University of Edinburgh in Scotland as part of an exchange program between the two universities. "It puts an extra year to your degree," says Verde, "but you really get a taste of what it means [to do] research."

For her Ph.D., Verde continued the work on dark matter that she started with Alan Heavens at Edinburgh. After receiving her Ph.D. in 2001, her "awesome boss" allowed her a great deal of freedom during her postdoc, which she used to split her time between Princeton and Rutgers University. "I was lucky enough that in my postdoc I could do whatever I wanted," Verde exclaims. "So I wasn't linked to a particular project." During her third year, she had the opportunity to work on a specific project--analyzing data from the Wilkinson Microwave Anisotropy Probe (WMAP)--for a year, which she calls the "opportunity of a lifetime."

Fortune Favors the Prepared

While she was at Rutgers, UPenn's department of physics and astronomy invited Verde to present a seminar; the department was so impressed by her presentation that they invited her to apply and interview for a faculty position. She got the job, beginning her first faculty appointment in 2003.

Verde had a much easier time finding a faculty position than most scientists do; in addition to UPenn, she was also courted for a faculty position at another university. She thinks the reason for her success was only partly because of the quality of her work. "Of course in order to secure a faculty position you have to be visible so you have to do really good work," she says. "Universities area looking for people that are willing to transmit what they've learned," Verde says. That's why she recommends that aspiring scientists present their work as often as possible.

Verde credits her success partly to the mentors who have nurtured her career skills and helped her with her science. "I've been extremely lucky because all my advisors, from my undergraduate to my postdoc advisor, have been great," she recalls. "It is extremely important to have a mentor, somebody that is in an advanced state of their career that is actually willing to try to understand you and your needs in order to guide you in a good direction."

Three Big Questions

Verde wants to study, and hopefully elucidate, three specific areas. "If I can make a dent in any of these three questions, I would be very happy."

The first area of Verde's interest is the surprising acceleration of the universe's expansion. She uses a simple comparison to illustrate her point. "When you're playing with a soccer ball, if you throw it up you don't expect it to keep going up. You expect it to slow down when it goes up." A likely reason for the accelerating rate of expansion is the theory of the existence of dark energy, but no one knows what it really is or how it works. Does dark energy exert itself evenly throughout the Universe--as suggested by Einstein's cosmological constant--or does it exert a differential effect? When it becomes available in 2006, Verde plans to use data from the Atacama Cosmology Telescope (ACT) in Chile to see how dark energy has affected the Universe's expansion and how it affects the evolution of large-scale, galactic structures.

Another mystery Verde would like to explain is the relationship between luminous matter (like stars and planets) and dark matter. "We have strong indications that most of the mass in the universe doesn't shine," she says. In 2001 and 2002, Verde collaborated with the two degree field (2dF) galaxy redshift survey team and found that clustering of luminous matter corresponds to dark matter clustering in a quantifiable way. "I think there may be enough data that we can go into the details of the relationship between clustering of dark matter and clustering of galaxies," Verde says.

Perhaps the greatest question of all is how the universe began, how it evolved, and how it will continue to evolve. "The inflationary paradigm"--the widely accepted theory that the early Universe, within a fraction of a second after the Big Bang, expanded trillions of times by a huge factor--"seems to work extremely well; can we know more about it?" Verde asks. She believes that if the Universe started out small and then suddenly expanded--as predicted by the inflationary paradigm--then questions related to quantum physics could be observable via cosmology. She and many other cosmologists believe there may be a fundamental theory that connects "quarks to the cosmos" on the large scale.

With so much still unknown about the Universe--dark matter and dark energy compose about 95% of it, according to current theories--there is plenty of room for discovery. And when you consider Verde's youth, initial success, and enthusiasm for her work, she may very well find answers to her questions about the nature of the Universe. If that happens, she won't be the only one happy about those discoveries.

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